In light-emitting diode chips, a comparatively thick current spreading layer composed of a semiconductor material having good electrical conductivity is generally arranged between the electrical contact and the light-emitting semiconductor layer sequence, in order to obtain as uniform a current flow as possible through the active layer.
By way of example, the document U.S. Pat. No. 6,426,518 B1 discloses a light-emitting diode chip wherein the light-emitting region is based on a phosphide compound semiconductor. A current spreading layer composed of p-AlGaAs is arranged between the electrical contact and the light-emitting region. The current spreading layer has a thickness of between 1 μm and 10 μm.
It has been found that with such comparatively thick current spreading layers composed of AlGaAs, a good current spreading layer can be obtained, but on the other hand a not inconsiderable proportion of the emitting radiation is also absorbed. The absorption by a thick current spreading layer is non-negligible in particular when the emitted radiation has a short wavelength and/or the proportion of aluminum in the current spreading layer is low. Furthermore, it has been found that an increase in the portion of aluminum in the current spreading layer increases the sensitivity of the light-emitting diode chip to moisture.